Personalized Melanoma Vaccine Cuts Recurrence Risk at 5 Years

A personalized mRNA vaccine kept melanoma from coming back in nearly 70% of high-risk patients five years after treatment, compared with 49% of those who received standard care alone, according to trial results presented at the American Society of Clinical Oncology’s annual meeting and published in the Journal of Clinical Oncology. The shot, built from each patient’s own tumor, was paired with the immunotherapy drug pembrolizumab, sold as Keytruda.

The signal is striking, and it comes from a small study. Only 157 patients took part, and the data that decides whether this becomes medicine, rather than a promising exception, sits in a much larger trial that will not report for years. That gap between an early result and a real verdict is the wager Moderna and Merck have placed.

The Five-Year Numbers That Strengthen the Case

At a median follow-up of just over 60 months, the combination of the vaccine and Keytruda reduced the risk of melanoma returning or the patient dying by 49% versus Keytruda alone (hazard ratio 0.510; 95% confidence interval 0.294 to 0.887; p=0.0075). The reduction in the risk of the cancer spreading to distant organs, or death, came in near 59%.

What caught oncologists’ attention was not the headline figure but its durability. The 49% risk reduction at five years was essentially unchanged from the three-year readout the same trial produced in 2024, when recurrence-free survival ran 74.8% against 55.6%. In a field where early benefits often fade, holding the line for two more years matters.

An exploratory look at overall survival pointed the same way (hazard ratio 0.471), though the wide confidence interval means it cannot yet be called proof. Here is how the two arms of the trial compared at the five-year mark.

Everyone in the study had at least stage 3 melanoma, meaning the cancer had reached nearby lymph nodes or skin and carried a high chance of returning even after the tumor was cut out. About half of such patients relapse within five years. “The treatments we have are not perfect. People relapse,” said Dr. Janice Mehnert, director of the melanoma and cutaneous medical oncology program at NYU Langone Health and the senior trial investigator.

How a Vaccine Built From One Tumor Works

The product, now called intismeran autogene and known in the lab as mRNA-4157 or V940, is not an off-the-shelf injection. Each dose is manufactured for a single person, using genetic material pulled from that patient’s removed tumor.

Cancer cells carry DNA mutations that produce unusual proteins on their surface, called neoantigens. Those flags are unique to the tumor, which makes them ideal targets: a healthy cell does not display them. The vaccine carries instructions for the immune system to recognize up to 34 neoantigens the researchers judged the best targets, then trains T-cells to hunt down any cancer cells still carrying those signatures.

The sequence runs like this:

1. Surgeons remove the tumor and send a sample for genetic sequencing.
2. Scientists scan the mutations and pick up to 34 of the strongest neoantigen targets.
3. A custom mRNA is synthesized, usually four to six weeks after surgery.
4. The patient receives up to nine doses, spaced about three weeks apart, timed to their pembrolizumab cycles.
5. Trained T-cells patrol for residual cells and any new ones that appear.

“It’s training the immune system to recognize the tumor signature long after the tumor is gone,” said Jeff Coller, a professor of RNA biology and therapeutics at Johns Hopkins University who was not involved in the research. The melanoma program began before the pandemic, but it leaned heavily on the mRNA manufacturing advances that the Covid years accelerated.

Decades of Cancer Vaccine Failures Set the Bar

The reason specialists are cautious rather than celebratory is history. Researchers have chased therapeutic cancer vaccines for a generation, and the graveyard of late-stage trials is crowded. Plenty of candidates looked good in small studies, then failed to show meaningful benefit once they reached the large, randomized tests that regulators require.

We have tried to use vaccines in cancer therapy for decades, but the efficacy has not been clinically relevant in phase 3 trials to date. If this is successful, this will open up a new field that will be relevant not just to melanoma, but many other cancers.

That was Dr. Shailender Bhatia, director of the melanoma team at Fred Hutch Cancer Center in Seattle, who was not part of the trial. His point frames the stakes precisely. The five-year melanoma data clears a bar that earlier vaccines reached too, the encouraging mid-stage signal. What none of them did was survive the jump to a definitive trial.

A Side-Effect Profile That Stands Apart

One result drew almost as much interest as the survival curves: the vaccine added benefit without piling on harm. Patients reported side effects similar to those from mRNA Covid shots, chills, headaches and flu-like symptoms that cleared in a day or two. The safety profile at five years held consistent with earlier reports, with no greater toxicity from adding the vaccine on top of immunotherapy.

That detail is more important than it sounds. Combining cancer drugs usually means trading extra side effects for any extra benefit, and often the side effects arrive without the benefit. “Generally what we have seen is that if we layer more drugs with immunotherapy, it causes more toxicity but not more benefit. So that is where the results of this trial are promising,” Bhatia said.

Mehnert’s team also found that patients whose cancer stayed away tended to mount the strongest immune response after vaccination, a thread of evidence linking the shot itself to the longer recurrence-free survival rather than to chance.

The Bet Now Riding on a 1,089-Patient Phase 3

The companies are not waiting to find out whether the melanoma signal generalizes; they are spending as if it will. Moderna and Merck have built an entire program, named INTerpath, around individualized neoantigen therapy (INT, the umbrella term for these tumor-specific vaccines), spanning eight phase 2 and phase 3 studies.

The centerpiece is INTerpath-001, a phase 3 trial in high-risk stage 2 to 4 melanoma. It is fully enrolled with about 1,089 patients across 14 countries, and its primary completion is estimated for late 2029. Beyond skin cancer, the wager extends to several other tumor types already in testing:

• Melanoma, the lead indication, in the 1,089-patient INTerpath-001 study.
• Non-small cell lung cancer (NSCLC, the most common form of lung cancer), in a separate phase 3 trial.
• Bladder cancer, in adjuvant testing after surgery.
• Renal cell carcinoma (RCC, the main type of kidney cancer).

Kyle Holen, M.D., Moderna’s senior vice president and head of development, said the five-year follow-up “highlights the potential of a prolonged benefit.” That is the company line, and the science behind it is real. It is also a bet whose payoff is years away and whose precedent is discouraging.

If INTerpath-001 reproduces the phase 2b signal across more than a thousand patients, the approach opens to the lung, kidney and bladder tumors already queued behind it, and a long-frustrated field finally has its template. If the effect thins out at scale, the way cancer vaccine benefits have thinned before, melanoma stays a hopeful exception and the larger promise waits for another decade’s technology.

Frequently Asked Questions

What Is Intismeran Autogene?

Intismeran autogene, also known as mRNA-4157 or V940, is an investigational personalized cancer vaccine developed by Moderna and Merck. It is made from genetic material in a patient’s own tumor and is designed to train the immune system to attack cancer cells carrying specific mutations. It is given alongside the immunotherapy drug pembrolizumab (Keytruda).

How Is a Personalized Cancer Vaccine Different From a Flu or Covid Shot?

A flu or Covid vaccine prevents infection and is identical for everyone. This cancer vaccine is therapeutic, given after a tumor is removed to stop it returning, and is manufactured individually for each patient based on the unique mutations in their tumor. It targets up to 34 of those tumor-specific markers, called neoantigens.

Is the Melanoma Vaccine Approved and Available?

No. It remains investigational and is available only through clinical trials. The five-year results come from a mid-stage phase 2b study of 157 patients, and regulators typically require a large, randomized phase 3 trial before approval. That decisive trial is fully enrolled but is not expected to complete its primary analysis until around 2029.

What Were the Five-Year Results?

About 70% of patients who received the vaccine plus Keytruda remained free of recurrence at five years, compared with 49% on Keytruda alone. The combination cut the risk of recurrence or death by 49% and the risk of distant metastasis or death by roughly 59%.

What Are the Side Effects?

Patients reported flu-like symptoms similar to those from mRNA Covid vaccines, including chills and headaches, that lasted a couple of days. Importantly, adding the vaccine did not increase toxicity compared with the immunotherapy alone, which is unusual when cancer treatments are combined.

Which Cancers Besides Melanoma Are Being Tested?

Under the INTerpath program, the same individualized neoantigen approach is being studied in non-small cell lung cancer, bladder cancer and renal cell carcinoma, across eight phase 2 and phase 3 trials in total.

the full five-year melanoma trial announcement, the phase 3 INTerpath-001 study record, and the published KEYNOTE-942 three-year update in the Journal of Clinical Oncology set out the underlying data. The result also lands amid a wider wave of pharmaceutical money flowing into vaccines, including Eli Lilly’s multibillion-dollar vaccine acquisitions, while prevention still matters most for a disease driven by ultraviolet exposure and skin cancer risk.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Intismeran autogene is an investigational therapy that has not been approved by regulators and is available only through clinical trials. Patients should consult a qualified oncologist before making any treatment decisions. All figures are accurate as of publication.